Why are coal, oil and natural gas called fossil fuels

Over millions of years, heat and pressure from Earth's crust decomposed these organisms into one of the three main kinds of fuel: oil (also called petroleum), natural gas, or coal. These fuels are called fossil fuels, since they are formed from the remains of dead animals and plants.

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when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.

i just learnt this recently but i need to look through my notes again